Brucella pinnipedalis infections in Pacific harbor seals in Washington State

This paper discusses Brucella pinnipedalis infections in harbor seals (Phoca vitulina) in Washington state and transmission to humans and other wildlife. The disease poses a threat to endangered populations and may be exacerbated by organic pollutants.

Brucella pinnipedalis was first identified in stranded harbor seals in 1994. Seals are thought to contract Brucella after weaning, in association with fish consumption and possibly lungworm infection. Contact with seals as well as consumption of raw fish are identified as potential vectors in human cases. Brucella can also be transmitted to other wildlife and domestic animals. The authors report that for the general public, the chances of contracting an infection are slim, but those working directly with seals are at risk of exposure.

[Editor's note: Symptoms of Brucella in humans include "undulant fever, tiredness, night sweats, headaches and chills" that may continue for several months and require medical treatment (Godfroid 2002).]

Infection is also a risk for animals that prey on seals, such as killer whales (Orcinus orca). The pathogen causes abcesses, bronchopneumonia, and lymphadenitis in pinnipeds, and in terrestrial vertebrates is associated with abortion and infertility. The most common finding in this study was verminous pneumonia due to Parafilaroides spp. or Otostrongulus circumlitus. In whales, research suggests that infection could reduce fecundity and slow the recovery of endangered populations.

The paper also shows an association between increased exposure and infection with Brucella in the region where persistent organic pollutants are highest (South Puget Sound), suggesting a potential toxicity mediated immune issue.